Please Excuse my ignorance here, I'm just seeking knowledge, not going to try and fix this thing by myself?
Just got this amplifier, it functions and sounds fine. The tremolo "intensity" pot had been disconnected, also the leads from the trem footswitch.
I am including here the schematics for this model?
There is a disconnected Green wire that you can see in the first pic I believe it goes to the foot switch control. The footswitch path is completed by continuing to ground?
The yellow and black wires that are disconnected from the "intensity" pot are a mystery to me. Yellow goes to one of the transistors I've circled in Photo 2?
One goes to a transistor at the power grid? (sounds scary to me).
I read at this forum that failed Oil Caps are often the cause of trem circuits failing in these amps?
Thanks
Univox Lafayette U-152 H-152 Tremolo questions
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Univox Lafayette U-152 H-152 Tremolo questions
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Stevem
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J
First off this is a tube amp, it has no Transistors in it like you posted about!
Yes,you can get a good shock from one of these when working on them unles you turn it off with the tubes installed as this wil power down that high voltage you need to watch out for!
In regards to getting that trem pot hooked back up just disregard the wire colors for now and learn to follow the schematic.
The wire coming off of the 47K resistor goes to the left hand terminal of the pot with the knob facing you.
The center terminal of the pot goes off to the junction of the two 220K grid resistors, and now you know where the other wire goes and that the cap goes across the left and right terminal of the pot.
Yes, these wonderful sounding oil caps fail due to there age and non use, those oil caps and power supply caps in the amp with a black band at one end should get replaced.
Before you work on the amp hook up your voltmeter set for DC volts across that first 450 volt filter off of the 6CA4 rectifier and confirm that the voltage had bled down to under 40 volts and you will be safe.
Yes,you can get a good shock from one of these when working on them unles you turn it off with the tubes installed as this wil power down that high voltage you need to watch out for!
In regards to getting that trem pot hooked back up just disregard the wire colors for now and learn to follow the schematic.
The wire coming off of the 47K resistor goes to the left hand terminal of the pot with the knob facing you.
The center terminal of the pot goes off to the junction of the two 220K grid resistors, and now you know where the other wire goes and that the cap goes across the left and right terminal of the pot.
Yes, these wonderful sounding oil caps fail due to there age and non use, those oil caps and power supply caps in the amp with a black band at one end should get replaced.
Before you work on the amp hook up your voltmeter set for DC volts across that first 450 volt filter off of the 6CA4 rectifier and confirm that the voltage had bled down to under 40 volts and you will be safe.
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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Stevem
- Posts: 5144
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
T
Note that the caps with a black band, or + makings at one end are of the electrolytic type, but only the caps that have a lead that goes to ground have to be replaced with such a type.
All of the other caps as the ones you need to replace in the Trem circuit to get it working again can be of the non electrolytic type, as in the easy to find and not too expensive Orange drop type, or even for this Trem circuit since it serves no audio function could be replaced with a even smaller cost Disc type rated for atleast 400 volts.
While you are ordering up parts it would also pay to replace the 5K ohm 10 watt resistor and the 300 ohm 10 watt resistor as these fail with age too and although they work now they could fail at any time!
All of the other caps as the ones you need to replace in the Trem circuit to get it working again can be of the non electrolytic type, as in the easy to find and not too expensive Orange drop type, or even for this Trem circuit since it serves no audio function could be replaced with a even smaller cost Disc type rated for atleast 400 volts.
While you are ordering up parts it would also pay to replace the 5K ohm 10 watt resistor and the 300 ohm 10 watt resistor as these fail with age too and although they work now they could fail at any time!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Univox Lafayette U-152 H-152 Tremolo questions
Thank you Stevem,
My brain knew resistor but my fingers typed transistor. I very much appreciate your posts and they will absolutely be read and studied!
Thanks again.
My brain knew resistor but my fingers typed transistor. I very much appreciate your posts and they will absolutely be read and studied!
Thanks again.
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Stevem
- Posts: 5144
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
J
Also note that the 50 volt 100 uf cap in the output stage is only bearly enough to reproduce the low E string so you might want to audition a 200 to 250 uf cap there if the amp sounds light on the bottom end with the neck pickup, but note more low end will push the output tubes into clipping sooner which could be good or bad.
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Univox Lafayette U-152 H-152 Tremolo questions
I played this little amp with a boost pedal this past Sunday at church, half expecting it to give up the ghost, fortunately it hung in there, sounded good. I believe I will set the amp to the side, order, and replace the atlas caps, those electrolytic caps, and the large resister before I worry about the tremolo circuit. I'll spend the week I wait for supplies becoming adept at draining the amplifier (caps) of any potential heart stoppage. Keeping my left hand in my pocket etc. I'll let you know if it sounds any different, or if I happen to end up with a soundless brick LOL. The guy who repackaged this thing made it tight and it was hot, power transformer didn't have room to breath, I added a computer fan, with whatever inherent dusty problems that will bring? Keeps much cooler.
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Stevem
- Posts: 5144
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
J
The fan is a great way to go!
In regards to the Tremolo you can do what I have done for people and install a switch to cut the power fed to the two 220k resistors that power the tube.
This wil free up a few milliamps and give the amp a touch more clean volume and punch if you find you want such!
In regards to the Tremolo you can do what I have done for people and install a switch to cut the power fed to the two 220k resistors that power the tube.
This wil free up a few milliamps and give the amp a touch more clean volume and punch if you find you want such!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!